Apparatus and methods for accessing and removing material from body lumens

ABSTRACT

An apparatus and method are provided for accessing and/or removing material from a body lumen. The apparatus includes a tubular sheath including a shaft having a proximal end and an expandable distal end that is expandable between a collapsed configuration and an expanded, tapered configuration. A treatment member can be introduced into the body lumen through the tubular sheath. The treatment member includes one or more expandable members to interact with the material to be removed from the body lumen.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/847,008, filed Sep. 8, 2015, and published as U.S. Patent App. Pub.No. 2015/0374404 on Dec. 31, 2015, which is a divisional of U.S. patentapplication Ser. No. 13/022,523, filed Feb. 7, 2011, and issued as U.S.Pat. No. 9,126,015 on Sep. 8, 2015, which is a continuation ofInternational Patent App. No. PCT/US2009/053237, filed Aug. 8, 2009, andpublished as International Patent App. Pub. No. WO 2010/017537 on Feb.11, 2010, which claims the benefit of U.S. Provisional Patent App. No.61/087,508, filed Aug. 8, 2008, the entire disclosures of which areexpressly incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates generally to apparatus for treatingobstructive material, e.g., thrombus, stenosis, and/or otherobstructions within a body lumen of a patient, e.g., within a tubulargraft, aorto-venous fistula, blood vessel, and the like. Moreparticularly, the present invention relates to apparatus for removing orotherwise capturing thrombus or other obstructive material within a bodylumen, and/or for dilating a body lumen, and to methods for making andusing such apparatus.

BACKGROUND

Flow within a blood vessel or other body lumen within a patient'svasculature may become constricted or ultimately interrupted for avariety of reasons. For example, a vessel may gradually narrow due toinflammation and/or cell proliferation. In addition, thrombus may formdue to such narrowing or other flow problems within a vessel.

For example, an aorto-venous graft may be implanted in an arm of apatient experiencing kidney failure, e.g., to facilitate dialysistreatment. Such grafts may be a fistula formed directly in the patient'sbody, e.g., through tissue between an adjacent artery and vein or othervessels, may be a xenograft implanted between two vessels, or may be asynthetic graft. Such grafts only have a limited life cycle due toinflammation, thrombus formation, and the like. Once such a graftbecomes sufficiently occluded or otherwise deteriorates, a new graftmust be implanted at a new location for subsequent treatment.

Accordingly, apparatus and methods for removing material fromaorto-venous grafts, blood vessels, or other body lumens and/orotherwise treating body lumens would be useful.

SUMMARY

The present invention is directed to apparatus for treating a body lumenof a patient, e.g., a tubular graft, aorto-venous fistula, blood vessel,and the like. More particularly, the present invention is directed toapparatus for removing or otherwise capturing thrombus or otherobstructive material within a body lumen, and/or for dilating a bodylumen, and to methods for making and using such apparatus.

In accordance with one embodiment, a system is provided for removingobstructive material from a body lumen that includes an elongate tubularmember including a proximal end, a distal end sized for introductioninto a body lumen, a lumen extending between the proximal and distalends, and an elongate treatment member insertable through the lumen andincluding an expandable treatment element selectively expandable fortreating one or more regions within a body lumen. For example, thetreatment element may be used to direct obstructive material into thetubular member lumen.

In an exemplary embodiment, the tubular member may include an annularexpandable member on the distal end that is expandable from a collapsedconfiguration to an expanded configuration wherein the expandable memberadopts a tapered shape that flares outwardly away from the distal end todefine an inlet that is larger than and communicates with the lumen, theexpandable member sized to engage a wall of a body lumen within whichthe expandable member is expanded.

For example, the expandable member may include an outer annular membranesurrounding an inner annular membrane, the outer and inner membranesbeing attached together and to the tubular member distal end such thatthe outer and inner membranes together define a substantially enclosedinterior. The tubular member may include an inflation lumencommunicating with the interior such that, when inflation media isdelivered via the inflation lumen into the interior, the expandablemember is expanded to the expanded configuration.

In an exemplary embodiment, the outer membrane may have a greater axiallength than the inner member such that proximal ends of the outer andinner membranes are spaced apart from one another along the distal endof the tubular member. For example, the proximal end of the outermembrane may be attached to the distal end of the tubular member at afirst location and the proximal end of the inner membrane may beattached to the distal end of the tubular member at a second locationdistal to the first location.

In addition or alternatively, the inner membrane may be more resistantto bending or compression than the outer membrane. For example, theinner membrane may include a reinforcement layer to increase theresistance of the inner membrane to bending or compression. Optionally,the tubular member may include an access port on the proximal endproviding access to the lumen for removing material therefrom.

In another option, the system may include one or more additionalcomponents. For example, a dilator may be disposed within the lumen ofthe tubular member such that a tapered distal tip extends beyond theexpandable member in the collapsed configuration to provide asubstantially smooth transition during introduction of the tubularmember into a body lumen. In an exemplary embodiment, the dilator mayinclude a recess adjacent the distal tip for receiving a distal end ofthe expandable member in the collapsed configuration. The dilator may beremovable proximally from the tubular member lumen after the tubularmember is introduced into a body lumen such that the treatment devicemay be inserted into the tubular member lumen. Optionally, the tubularmember may include an expandable section including at least the distalend that is expandable from a relaxed size to an enlarged size toaccommodate receiving material larger than the relaxed state directedinto the lumen by the treatment device. For example, the tubular membermay be expandable along the entire length between the proximal anddistal ends.

In an exemplary embodiment, the expandable section of the tubular membermay include an elastic layer coupled to an inelastic layer including oneor more slots therein to accommodate the inelastic layer expanding, theelastic layer biasing the expandable section to return towards therelaxed size. For example, the elastic layer may include an elasticsleeve surrounding the inelastic layer. In addition or alternatively,the inelastic layer may include a tubular body and wherein the one ormore slots comprise one or more longitudinal slots extending along thelength of the tubular body. Alternatively, the inelastic layer mayinclude a tubular body and the one or more slots may include a pluralityof longitudinal slots spaced apart axially and circumferentially fromone another along the length of the tubular body.

In any of these embodiments, the treatment element of the treatmentdevice may include a first non-compliant balloon mounted on a distal endof the treatment device. In addition or alternatively, a secondcompliant balloon may be mounted on treatment device, e.g., over thefirst balloon.

In addition or alternatively, the treatment device comprises a tractionmember at least partially covering the treatment element. For example,the traction member may be movable between a first position wherein thetraction member is disposed adjacent the treatment element and a secondposition wherein the traction member at least partially covers thetreatment element. In an exemplary embodiment, the traction member mayinclude an expandable mesh.

In accordance with another embodiment, an apparatus is provided forproviding access to a body lumen that includes an elongate tubularmember comprising a proximal end, a distal end sized for introductioninto a body lumen, and a lumen extending between the proximal and distalends; and an annular expandable member on the distal end that isexpandable from a collapsed configuration to an expanded configurationwherein the expandable member adopts a tapered shape that flaresoutwardly away from the distal end to define an inlet that is largerthan and communicates with the lumen, the expandable member sized toengage a wall of a body lumen within which the expandable member isexpanded.

In accordance with yet another embodiment, an apparatus is provided forremoving obstructive material from a body lumen and for dilating thebody lumen. For example, the apparatus may include an outer tubularmember having a proximal end, an expandable distal end, and a firstlumen extending between the proximal and distal ends. The apparatus mayalso include an inner member comprising a proximal end and a distal endhaving a tapered profile, wherein the inner member is configured forbeing slidably disposed within the first lumen of the outer member suchthat the inner member proximal end extends proximally from the outermember proximal end and the inner member distal end extends distallyfrom the outer member distal end. Optionally, the inner member may havean undercut configured for engaging the outer member distal end when theouter member distal end is in an unexpanded configuration. In additionor alternatively, the apparatus may include an elongate memberconfigured for being slidably disposed within the first lumen of theouter member. The elongate member may include two concentric balloons ona distal end thereof, wherein one of the balloons is more compliant thanthe other balloon. For example, the less compliant balloon may beconfigured for dilating the body lumen.

In one embodiment, the distal end of the outer member may include aninner membrane, an outer membrane, and a cavity between the inner andouter membranes. Optionally, the inner membrane may include areinforcement layer that allows radial expansion and resists bendingand/or compression in an axial direction. The inner membrane may have ashorter length than the outer membrane or they may have similar lengths.The outer member may further include a second lumen extending betweenthe outer member proximal and distal ends and communicating with thecavity.

The outer member expandable distal end may have an expandedconfiguration wherein a distal opening of the outer member has a firstdiameter, and the distal end tapers from the first diameter proximallytowards a second diameter, wherein the first diameter is larger than thesecond diameter. For example, the first diameter may be adjustable suchthat the distal opening may be substantially equal to an inner diameterof a body lumen within which the expandable distal end is expanded.

In accordance with still another embodiment, an apparatus is providedfor treating a body lumen. The apparatus includes an tubular sheathhaving a proximal end, an expandable distal end having an expandedconfiguration and an unexpanded configuration, a shaft extending betweenthe proximal and distal ends, and a first lumen extending between theproximal end and a distal opening in the distal end, wherein, when thedistal end is in the expanded configuration, the distal end tapers froma first diameter at the distal opening to a second diameter of theshaft, wherein the first diameter is larger than the second diameter.

Optionally, the apparatus may also include a dilator slidably disposedwithin the first lumen of the sheath. The dilator includes a proximalend adjacent the sheath proximal end, a distal end extending from thesheath distal end and having a tapered distal tip, and an annular regionadjacent the distal tip for receiving the sheath distal end when thesheath distal end is in the unexpanded configuration, e.g., to provide asubstantially smooth transition between the distal tip and the sheath.

In accordance with yet another embodiment, an apparatus for treating abody lumen is provided that includes a tubular member including aproximal end, an expandable distal end, a first lumen extending betweenthe proximal and distal ends, and a second inflation lumen extendingbetween the proximal and distal ends, wherein the distal end, in anexpanded configuration, has a tapered profile that tapers from a firstdiameter at a distal opening proximally towards a second diameter,wherein the first diameter is greater than the second diameter.

In one embodiment, the tubular member distal end may include an innermembrane, an outer membrane, and a cavity between the inner membrane andthe outer membrane, and the second lumen may communicate between thecavity and an inflation port on the tubular member proximal end.Optionally, the inner membrane may include a reinforcement layer. Thereinforcement layer may be formed of a material that is resistant tobending and/or compression in an axial direction relative to the tubularmember. In addition or alternatively, the outer membrane may have alength that is greater than a length of the inner membrane or thelengths may be substantially the same. For example, when the tubularmember distal end is in the expanded configuration, the inner membranemay have a concave configuration and the outer membrane may have aconvex configuration.

Optionally, the apparatus may also include an inner member slidablydisposed within the first lumen of the tubular member. The inner memberincludes a proximal end adjacent the tubular member proximal end, and adistal end extending from the tubular member distal end and having atapered distal tip. The inner member distal end may include an annularundercut having an opening facing towards the inner member proximal end,wherein the tubular member distal end, in an unexpanded configuration,may fit within the opening.

In addition or alternatively, the apparatus may further include anelongate member configured for being slidably disposed within thetubular member first lumen. The elongate member may include one or moreexpandable members on a distal end thereof, e.g., a single balloon orconcentric balloons, e.g., where the outer balloon is more compliantthan the inner balloon.

In accordance with another embodiment, a method for treating a bodylumen is provided that includes introducing a flow restoration apparatusinto the body lumen, wherein the flow restoration apparatus comprises anouter member and an inner member disposed within a lumen of the outermember; expanding a distal end of the outer member from an unexpandedprofile to a tapered, expanded profile, e.g., such that the outer memberdistal end engages or otherwise contacts an inner wall of the bodylumen; and withdrawing the inner member from the outer member, therebyleaving the outer member in the expanded configuration disposed withinthe body lumen.

A procedure may then be performed via the outer member, e.g., to removeor otherwise treat obstructive material within the body lumen. Forexample, an elongate treatment member may be introduced through theouter member and into the body lumen and manipulated to capture orremove material within the body lumen. In one embodiment, a distal endof the treatment member may be advanced from the expanded distal end ofthe outer member and beyond material to be removed. A first expandablemember on the treatment member distal end may be expanded, and thetreatment member may be withdrawn towards the outer member to directmaterial in the body lumen into the outer member expanded distal end,e.g., by pulling the expanded first expandable member entirely into theouter member. Optionally, an additional obstruction within a portion ofthe body lumen may be located, and a second expandable member on thetreatment member distal end may be expanded to dilate the portion of thebody lumen.

Other aspects and features of the present invention will become apparentfrom consideration of the following description taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

It will be appreciated that the exemplary apparatus shown in thedrawings are not necessarily drawn to scale, with emphasis instead beingplaced on illustrating the various aspects and features of theillustrated embodiments.

FIG. 1A is a cross-sectional view of a first exemplary embodiment of aflow restoration apparatus or system, including an outer sheath and adilator, disposed within a body lumen.

FIG. 1B is a detail of a distal portion of the apparatus shown in FIG.1A.

FIG. 2A is a cross-sectional view of the apparatus of FIG. 1A, showingan expandable member on the sheath in an expanded configuration withinthe body lumen.

FIG. 2B is a detail of a wall of the expandable member shown in FIG. 2A.

FIG. 3 is a cross-sectional view of the apparatus of FIGS. 1A and 2Awith the expandable member in the expanded configuration and the dilatorremoved.

FIG. 4 is a cross-sectional view of a patient's body showing anexemplary dialysis graft extending between a vein and an artery, andincluding obstruction material within the graft lumen.

FIGS. 5-10 are a cross-sectional views of the dialysis graft of FIG. 4,showing an exemplary method of removing obstructive material from thegraft lumen.

FIGS. 11-12 are cross-sectional views of the dialysis graft of FIG. 4,showing a method for dilating an occluded region of the graft.

FIG. 13 is a perspective view of an alternative embodiment of a sheaththat may be included in the flow restoration apparatus and methods ofFIGS. 1A-12.

FIG. 14A is a side view of an alternative embodiment of a ballooncatheter that may be used in the methods shown in FIGS. 5-12.

FIGS. 14B-14D are side views of another alternative embodiment of theballoon catheter shown in FIG. 14A.

FIGS. 15A and 15B are cross-sectional views of a second exemplaryembodiment of a flow restoration apparatus including an outer sheath anda guidewire.

FIG. 16A is a cross-sectional view of a third embodiment of a flowrestoration apparatus including an outer sheath carrying an expandablemember and having an expandable wall, and a balloon catheter.

FIG. 16B is a cross-section of the sheath of FIG. 16A taken along line16B-16B.

FIG. 16C is a detail of an alternative embodiment of the sheath of FIG.16A, including slots for providing an expandable wall.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Turning to the drawings, FIGS. 1A-3 show a flow restoration apparatus 10for providing access and/or treating a body lumen 50, e.g., for removingthrombus, objects, debris, and/or obstructive material from within thebody lumen 50, and/or for dilating region of the body lumen 50, e.g., ablood vessel, aorto-venous fistula, tubular graft, and the like.Generally, the apparatus 10 includes an outer sheath or other tubularmember 20, and, optionally, a dilator or other inner member 30, whichtogether with one or more treatment apparatus (not shown), describedfurther below, may provide a system for removing obstructive materialand/or otherwise treating occluded regions within body lumens in apatient's body. In addition, such a system may include one or moreadditional components, e.g., one or more guidewires, syringes or othersources of inflation media and/or vacuum, and the like, such asguidewire 64 and syringe 18, as shown in FIG. 7 and described furtherbelow.

With additional reference to FIGS. 6-9, the sheath 20 is an elongatetubular body or shaft 22 including a proximal end 22 a, a distal end 26,and a lumen 24 (best seen in FIGS. 1A-3) extending therebetween. Thedistal end 26 may be expandable, i.e., movable between a collapsedconfiguration (as shown in FIGS. 1A and 1B) and an expandedconfiguration (as shown in FIGS. 2A and 3), e.g., in which theexpandable distal end 26 has a tapered profile or transition. In theembodiment shown, the distal end 26 includes a balloon or otherexpandable member 26 a attached to and/or extending from the distal end26 of the shaft 22 to provide an expandable transition, as describedfurther below.

Optionally, a handle or hub 13 may be coupled to or otherwise providedon the proximal end 22 a of the sheath 20, e.g., for manipulating thesheath 20 and/or the entire apparatus 10. The handle 13 may have anergonomic shape, e.g., to facilitate holding and/or manipulating thehandle 13. The handle 13 may include one or more ports, e.g., side port14, for coupling one or more fluid sources to the apparatus 10, such asa source of inflation media, a source of vacuum, and/or a source ofdiagnostic and/or therapeutic agents (not shown). The side port 14 mayinclude one or more connectors (not shown) to facilitate coupling one ormore sources of fluid to the side port 14, e.g., a Luer lock connector,and/or one or more seals, e.g., a hemostatic seal, to prevent fluid fromleaking from the side port 64. In addition, the handle 13 may include aport 15 communicating with the lumen 24, e.g., for receiving the dilator30, a guidewire or other device (not shown) into and/or through thelumen 24. The port 15 may include one or more seals, e.g., a hemostaticseal (not shown), to accommodate passage of the dilator 30 or otherdevice therethrough without risk of substantial risk of leakage of bloodor other body fluids from the lumen 24.

The sheath 20 may have a substantially uniform construction along itslength, or alternatively, the construction may be varied. For example, aproximal portion of the sheath 20 may be substantially rigid orsemi-rigid to facilitate advancement of the apparatus 10 by pushing orotherwise manipulating the proximal end 22 a. In addition oralternatively, a distal portion of the sheath 20 may be flexible, e.g.,to facilitate bending and/or advancement through tortuous anatomywithout substantial risk of kinking or buckling. In exemplaryembodiments, the sheath 20 may be formed from materials such as metal,plastic, e.g., PEEK, Grilamed L25, and the like, or composite materials.The sheath 20 may have a length between about five and one hundredthirty centimeters (5-130 cm) and an outer diameter between about 1.6 to2.0 millimeters, and the lumen 24 may have a diameter between about 1.4and 1.8 millimeters.

Returning to FIGS. 1A-3, the dilator 30 may be removably disposed withinthe lumen 24 of the sheath 20, and generally includes a shaft 32including a proximal end 32 a (not shown, see FIG. 6), a distal end 32 bterminating in a tapered distal tip 36, and an accessory lumen 34extending the proximal and distal ends 32 a, 32 b. The distal tip 36 mayprovide a substantially atraumatic transition for facilitatingintroduction of the apparatus 10 through skin, vessel walls, and othertissues and/or advancement within a body lumen. The tapered distal tip36 may also provide a smooth transition between a guidewire and theouter sheath 20. The shaft 32 of the dilator 30, although flexible toaccommodate bending, may be more rigid than the shaft 22 of the sheath20 such that the dilator 30 may provide columnar support to the sheath20 as it is advanced during introduction or subsequent manipulation.

As best seen in FIGS. 1A and 1B, the distal tip 36 of the dilator 30extends distally from the distal end 26 of the sheath 20. The distal tip36 of the dilator 30 may include an annular undercut or other region 38at the proximal end of the distal tip 36, thereby defining an opening orrecess 37 that faces towards the proximal end 32 a of the dilator 30.When the dilator 30 is disposed within the lumen 24 of the sheath 20 andthe expandable member 26 a is in its collapsed configuration, a distalend 28 of the expandable member 26 a may be received in the recess 37,as shown in FIGS. 1A and 1B. In this manner, the region 38 may provide asubstantially smooth transition between the dilator 30 and the sheath 20for facilitating passage of the apparatus 10 through tissue. The region38 may also retain the expandable member 26 a against the dilator 30,e.g., to prevent proximal migration of the expandable member 26 a duringadvancement, which may otherwise cause the expandable member 26 a tobunch up or compress axially.

In the embodiment shown in FIGS. 1A-3, the expandable member 26 aincludes an outer annular membrane or surface 23 and an inner annularmembrane or surface 25 together defining a substantially enclosedinterior or region 27 therebetween. A lumen (not shown) may extend fromthe inflation port 14 on the handle 13 through the proximal end 22 a(not shown, see FIGS. 6-9) of the sheath 20 to the distal end 26 of thesheath 20, e.g., along a wall thereof, that communicates with theinterior 27. As shown in FIGS. 6-9, a source of inflation media orvacuum, e.g., a syringe 18, may be coupled to the inflation port 14,such that the interior 27 of the expandable member 26 a may be in fluidcommunication with the source 18 a to allow inflation media, e.g.,saline, water, and the like, to be delivered into and evacuated from theinterior 27 of the expandable member 26 a.

The outer and inner membranes 23, 25 may be formed from a single sheetor multiple sheets of material that may be bonded or otherwise attachedtogether into annular sleeves, e.g., by bonding with adhesive, sonicwelding, heat fusing, and the like, to substantially seal and/or enclosethe interior 27. Alternatively, the outer and inner membranes 23, 25 maybe formed as sleeves, e.g., by extrusion, injection molding, and thelike. In the embodiment best seen in FIG. 1B, the outer and innermembranes 23, 25 may be formed as separate sleeves of material whoseproximal and distal edges are attached together and/or to the distal end26 of the sheath 20 to define the expandable member 26 a. The membranes23, 25 may be formed from substantially inelastic or noncompliantmaterials, e.g., such that the expandable member 26 a expands to apredetermined size and/or shape upon inflation.

For example, the outer and inner membranes 23, 25 may be attachedtogether at a distal bond location 42 (best seen in FIG. 1B) andattached to the distal end 26 of the shaft 22 at proximal bond locations44, 46, respectively (best seen in FIGS. 1A and 2). For example distaledges of the outer and inner membranes 23, 25 may be lapped or buttedtogether. The proximal edge of the outer membrane 23 may be attached toan outer surface of the shaft 22, while the proximal edge of the innermembrane 25 may be attached to an outer surface of the shaft 22, to aninner surface of the first lumen 24, or butted to the distal end 26.

As shown in FIGS. 1A and 2A, the proximal bond locations 44, 46 may bespaced apart axially from one another, although alternatively, theproximal edges of the outer and inner membranes 23, 25 may be attachedto the distal end 26 at the same or similar axial locations, e.g., withthe outer membrane 23 attached over the inner membrane 25. In thecollapsed configuration, the outer and inner membranes 23, 25 may extendsubstantially axially with the outer membrane 23 substantiallysurrounding the inner membrane 25.

As shown in FIGS. 1A and 2, the outer membrane proximal bond location 46is further from the distal end 28 of the expandable member 26 a than theinner membrane proximal bond location 44. This may promote a desiredshape for the expandable member 26 a in the expanded configuration,e.g., providing a substantially continuous tapered internal diametercommunicating with the lumen 24 of the sheath 20, as shown in FIG. 2A.For example, the tapered expanded profile may be due to the outermembrane 23 having a longer chord length between its proximal and distalbonding locations 46, 42 than that of the inner membrane 25. Uponinflation, the greater chord length of the outer membrane 23 maygenerate greater tension in the outer membrane 23 than in the innermembrane 25 with its shorter chord length. To balance these tensions,the expandable member 26 a of the sheath 20 may expand radiallyoutwardly in a curved or conical shape to reduce the tension in theouter membrane 23. Thus, when the expandable member 26 a is expanded tothe expanded configuration, the diameter of the inner membrane 25 (theinner diameter of the expandable member 26 a) may taper from arelatively large distal diameter D₁ at distal opening 21 to a relativelysmall proximal diameter, D₂. The material and size of the expandablemember 26 a may be selected such that the relatively large distaldiameter D₁ is substantially equal to or greater the inner diameter of abody lumen 50 within which the apparatus 10 is introduced, as explainedfurther below.

The expandable member 26 a of the sheath 20 may be expanded byintroducing inflation media into the interior 27 defined by the outerand inner membranes 23, 25. FIG. 2A shows the apparatus 10 after theexpandable member 26 a has been fully inflated. During the ballooninflation, the distal end 28 of the expandable member 26 a may flareradially outwardly away from a central longitudinal axis of the sheath20 and become free from the recess 38 in the dilator 30. The inflationpressure may exert a tension on the outer membrane 23 that causes it toexpand away from the longitudinal axis of the sheath 20. Tension mayalso be exerted on the distal bond location 42 and proximal bondlocations 44, 46. The proximal bond locations 44, 46 do not undergo asubstantial shape change in response to the applied tension because theyare bonded to the sheath shaft 22, which does not allow radialexpansion. The distal bond location 42 is pulled by the tension on theouter membrane 23 in a radially outward direction as the expandablemember 26 a expands to the expanded configuration.

To further enhance the expandable member 26 a adopting a tapered shapein the expanded configuration, different materials may be provided forthe outer and inner membranes 23, 25. For example, the inner membrane 25may be more rigid than the outer membrane 23, e.g., by providing adifferent relatively stiff material, a similar but greater thicknessmaterial, and the like for the inner membrane 25. Optionally, as shownin FIG. 2B, the inner membrane 25 may include a reinforcement layer 29to create or enhance adoption of the tapered shape. For example, stripsof material (not shown), e.g., hard plastic such as nylon or PEEK, ormetal, such as stainless steel or Nitinol, may be bonded, embedded, orotherwise attached to the inner membrane 25 such that the strips extendsubstantially axially at least partially between the proximal and distalbond locations 44, 42. Alternatively, a braid or other mesh (not shown)may be embedded within or attached to an inner or outer surface of theinner membrane 25. The reinforcement layer 29 may be substantiallyuniform or different along the axial length of the inner membrane 25.For example, the reinforcement layer 29 may increase the rigidity of theinner membrane 25 adjacent the proximal bond 44 relative to the regionadjacent the distal bond 42, if desired, e.g. to enhance the innermembrane 25 expanded into a bell shape during expansion of theexpandable member 26 a.

In addition or alternatively, the material of the reinforcement layer 29may allow radial expansion, while resisting bending or compression ofthe inner membrane 25 axially relative to the longitudinal axis of thesheath 20. For example, the combination of the reinforcement layer 29and the proximal bond locations 44, 46 may cause the expandable member26 a to adopt a pointed oval or almond shape in cross-section in theexpanded configuration, as shown in FIGS. 2A and 3. For example, theinner membrane 25 may have define a bell shape, e.g., having a concavecross-section, or may have a substantially straight conical shape whenthe inner membrane 25 flares or tapers. The tapered shape of theexpandable member 26 a may be advantageous for removing debris from abody lumen 50 because of the resulting relatively large diameter inlet21 that may funnel material into a relatively small lumen 24 for removalfrom the body lumen, as described further below.

Once the expandable member 26 a is expanded and the distal end 28 leavesthe recess 37 of the dilator 30, the dilator 30 is free to be withdrawnproximally from the sheath 20. The expanded sheath 20 with the dilator30 removed is shown in FIG. 3. Thrombus and other unwanted materialswithin a body lumen 50 within which the sheath 20 is deployed may thenbe swept into the lumen 24 of the sheath 20 via the tapered inlet 21, asdescribed in more detail below.

For example, turning to FIGS. 4-10, the apparatus 10 may be used toprovide access and/or removing thrombus or other material within oradjacent a dialysis or other tubular graft. Although the method of usingthe apparatus 10 is shown and described below as taking place within atubular graft, the apparatus 10 is not restricted to use within such agraft and may be used other body lumens within a patient's body, such asan aorto-venous fistula, xenograft, blood vessel, and the like.

An exemplary graft lumen 50 is shown in FIG. 4, which extends between anartery 51 and a vein 53, e.g., within a patient's arm or other locationwithin a patient's body. Thus, the graft lumen 50 may connect to thearterial blood flow through an arterial anastomosis 52, and to thevenous blood flow through a venous anastomosis 54. As is common indialysis graft failures, FIG. 4 shows that the venous anastomosis 54 isnarrowed due to the presence of a stenosis 56, which may be caused byinflammation and cell proliferation (also known as neointimalhyperplasia). A second stenosis 57 is shown in the mid-graft area.Additionally, a thrombus 58 is shown formed at the arterial anastomosis52, e.g., due to the slowed blood flow through the graft lumen 50 as aresult of the stenoses 56, 57 present.

Initially, as shown in FIG. 5, a needle 62 may be inserted through thepatient's skin and into the graft lumen 50. A guidewire 64 may then beadvanced through the needle 62 and into the graft lumen 50 for somedistance, e.g., to provide mechanical stability during subsequentinstrument introduction.

Next, as shown in FIG. 6, the apparatus 10 may be introduced over theguidewire 64 and into the graft lumen 50. The apparatus 10 may beprovided from the manufacturer with the dilator 30 loaded into thesheath 20, as shown in FIGS. 1A and 6. Alternatively, the dilator 30 maybe loaded into the sheath 20, e.g., by inserting the distal tip 36 intothe port 15 immediately before the procedure. In this alternative, thedilator 30 may be advanced such that the distal tip 36 passes beyond thedistal end 28 of the expandable member 26 a, and the dilator 30 may bewithdrawn to capture the distal end 28 in the recess 37. In anotheralternative, the annular region 38 and recess 37 may be omitted from thedilator 30 and the dilator 30 may simply pass through and extend beyondthe expandable member 26 a and distal end 26 of the sheath 20.

With the apparatus 10 assembled, the guidewire 64 may be backloadedthrough the distal tip 36 of the dilator 30 into the accessory lumen 34and out the proximal hub 39. The apparatus 10 may then be advanced overthe guidewire 64 through the skin and any intervening tissue into thegraft lumen 50 with the expandable member 26 a in the collapsedconfiguration until the expandable member 26 a is received completely inthe graft lumen 50, as shown in FIG. 6. Optionally, the dilator 30and/or expandable member 26 a may include one or more markers (notshown), e.g., one or more radiopaque bands or other markers, such thatexternal imaging, e.g., fluoroscopy, x-ray imaging, ultrasound, and thelike may be used to position the expandable member 26 a to a desiredposition within the graft lumen 50.

Turning to FIG. 7, with the sheath 20 in a desired position within thegraft lumen 50, the distal end 26 of the sheath 20 may be expanded. Withthe distal end 28 of the expandable member 26 a removed from the region37, the dilator 30 may be removed from the graft lumen 50 and sheath 20.Alternatively, if the dilator 30 does not include the annular region 38and recess 37, the dilator 30 may be removed before the expandablemember 26 a is expanded.

As shown in FIG. 7, a syringe 18 may be coupled to the inflation port 14to expand the distal end 26 of the sheath 20 via an inflation lumen (notshown) within the wall of the sheath 20 that allows fluid communicationwith the interior 27 (shown in FIGS. 1A-3) of the expandable member 26a.

The expandable distal end 26 a of the sheath 20 may provide severaladvantages over existing non-expanding sheaths. First, because theexpanded diameter D₁ of the distal end 26 is substantially equal to orgreater than the inner diameter of the graft lumen 50, the expandedexpandable member 26 a may form a seal with the graft lumen 50, therebypreventing blood flow and lowering the chances of embolization ofthrombus or other particles to the rest of the body during theprocedure. Second, the gradual tapered internal diameter of theexpandable member 26 a may facilitate removal of material from the graftlumen 50 by providing a funnel or gradual, smooth taper. Third, theexpandable member 26 a may substantially stabilize the sheath 20 withinthe graft lumen 50 by the traction between the expandable member 26 aand the wall of the graft lumen 50, e.g., to prevent undesired migrationof the sheath 20 during the procedure.

Next, as shown in FIG. 8, with the expandable member 26 a of the sheath20 expanded and the dilator 30 removed, one or more treatment devicesmay be introduced via the sheath 20 into the graft lumen 50, e.g., toperform one or more diagnostic and/or therapeutic procedures. As shownin FIG. 8, a balloon catheter 82 may be inserted over the guidewire 64and through the lumen 24 of the sheath 20, into the graft lumen 50,e.g., to a position on the far side of the material forming stenosis 57and thrombus 58. The catheter 82 may include a guidewire lumen (notshown) extending between a proximal hub or handle 90 on a proximal end82 a of the catheter 82 and a distal end 82 b of the catheter 82, i.e.,for use as an over-the-wire system (shown). Alternatively, the guidewirelumen in the catheter 82 may extend from the distal end 82 b to anintermediate location (not shown), e.g., for use as a rapid-exchangesystem.

In one embodiment, the balloon catheter 82 may be a low-pressureembolectomy catheter, e.g., including a compliant balloon on the distalend 82 b, e.g., as shown in FIG. 14A. However, in the exemplaryembodiment shown in FIG. 8, the balloon catheter 82 may include multipleballoons or expandable members to provide a multiple purpose device. Forexample, as shown, two concentric balloons 84, 86 may be provided on thedistal end 82 b of the balloon catheter 82. A first, non-compliant, highpressure balloon 84 may be bonded or otherwise attached to the shaft ofthe catheter 82. The non-compliant balloon 84 may be in independentfluid communication with a first inflation port 88 on the hub 90, e.g.,to which a syringe or other source of inflation media 18 a may becoupled. A second, compliant, low-pressure balloon 86 may be bondedconcentrically over the non-compliant balloon 84. The compliant balloon86 may be in independent fluid communication with a second inflationport 92 on the catheter hub 90, e.g., to which a syringe or other sourceof inflation 18 b may be coupled.

Turning to FIG. 9, with the catheter 82 in place with the distal end 82b within the artery 51 or otherwise beyond the thrombus 58, thecompliant balloon 86 may be expanded. The fluid and obstructive material(e.g., stenosis 57 and thrombus 58) within the graft lumen 50 may thusbe substantially isolated between the sheath 20 and the compliantballoon 86, e.g., substantially reducing the chance of material beingembolized into the artery 51, vein 53 and/or elsewhere in the body.

As shown in FIG. 10, the balloon catheter 82 may then be retractedproximally towards the sheath 20, pulling thrombus or other obstructivematerial with it. Optionally, the balloon catheter 82 may be pulledcompletely into and through the sheath 20, e.g., to substantially reducethe risk of the material becoming lodged in or otherwise occluding thesheath lumen 24.

All of the unwanted material may not be removed in a single pass of thecompliant balloon 86. For example, as shown in FIG. 10, a portion of themid-graft stenosis 57 may remain attached to the lumen wall. For thisreason, multiple passes may be completed, e.g., collapsing the compliantballoon 86, advancing the balloon catheter 82, expanding the compliantballoon 86, and pulling the balloon catheter 86 one or more additionaltimes, as desired. Optionally, any stenosis, thrombus, or other debris(e.g., stenosis 56) that was not reachable due to the orientation of thesheath 20 towards the artery 51 may be removed by removing the apparatus10 and introducing the apparatus 10 (or another new apparatus with adilator placed within a sheath, not shown) in the opposite directionwithin the graft lumen 50.

Some obstructions such as the mid-graft stenosis 57, shown in FIG. 10,may not completely removed by the compliant balloon 86. To address anystenosis that does not respond to balloon embolectomy, a high pressuredilation of the stenosis may be performed, as discussed in furtherdetail with reference to FIGS. 11-12. The apparatus 10 along with thedual-balloon catheter 82 may offer an improved method of performingdilation because of the dual balloon construction.

First, as shown in FIG. 11, the compliant balloon 86 may be inflatedwith a contrast solution and moved axially within the lumen 50. When theballoon 86 encounters the stenosis 57, it deforms to adopt the shape ofthe stenosis 57, as shown, which may be visible via fluoroscopy or otherexternal imaging. In addition, when the compliant balloon 86 encountersthe stenosis 57 during retraction, a greater resistance may be felt thanwhen moving the balloon 86 in an unobstructed vessel, giving the usertactile feedback as well as or instead of the external imaging. Thus,using visual and/or tactile feedback, the compliant balloon 86 may beaccurately positioned over the stenosis 57, as shown in FIG. 11.

Turning to FIG. 12, with the balloon catheter 82 in the positionidentified using the compliant balloon 86, the non-compliant balloon 84may then be inflated to dilate the stenosis 57. The compliant balloon 86may deflated substantially simultaneously with inflation of thenon-compliant balloon 84 or immediately before inflation. Thus, thestenosis 57 may be dilated, as shown, leaving a substantiallyunobstructed graft lumen 50.

One of the advantages of this dilation procedure over conventionaldilation procedures is that that the stenosis 57 may easily and directlybe located using the same catheter 82 that will be used for dilation,thereby eliminating catheter exchanges otherwise needed to replace theballoons. Another advantage is that no contrast solution is releasedinto the bloodstream of the patient during this dilation procedure. Manypatients have problems tolerating contrast solutions, especially thosepatients with compromised kidney function, and therefore may benefitfrom the dilation procedure described above.

In further alternatives, other devices may be introduced using theapparatus 10, e.g., to perform a procedure within the graft lumen 50 orat other locations within a patient's body where the sheath 20 isdeployed. Exemplary apparatus and methods that may be used are disclosedin applications, Serial Nos. 61/099,171, filed Sep. 22, 2008,61/143,603, filed Jan. 9, 2009, 61/152,227, filed Feb. 12, 2009, Ser.No. 12/480,664, filed Jun. 8, 2009, Ser. No. 12/497,135, filed Jul. 2,2009, and in International Publication No. WO 2009/076482. The entiredisclosures of these references are expressly incorporated by referenceherein.

During removal of stenosis or thrombus, e.g., using any of the apparatusand methods described herein, it may be desirable to unclog or preventclogging of the sheath. To facilitate this, it may be desirable toprovide an access port into the proximal end of the sheath. Turning toFIG. 13, a sheath 20′ is shown, which may be similar to that shown inFIGS. 1A-3 and described elsewhere herein, which may include a door 102in its handle 13.′ The door 102 may be opened by a user, e.g., at anytime during a procedure, so that thrombus or other material 104 drawninto the sheath 20′ may be manually removed from the handle 13,′ e.g.,if the sheath 20 becomes clogged. Alternatively, other types ofrepeatably openable and closeable access ports or structures may beprovided instead of the door 102, e.g., a breach or other slidablemechanism (not shown), which may provided on the handle 13′ or elsewhereon the sheath 20.′ In a further alternative, the handle 13′ may have acompartment (not shown) into which material (e.g., thrombus 104) may bepushed, e.g., when the material is withdrawn proximally through thesheath 20,′ e.g., using the balloon 86 of the balloon catheter 82 orother device described herein.

Turning to FIGS. 14B-14D, another embodiment of a treatment device isshown that may be included with the apparatus 10 to provide a system fortreating a body lumen. In this embodiment, a balloon catheter 82′ isshown that may be introduced through the sheath 20 (not shown, see FIGS.1A-3) to remove thrombus or other material from a graft or other bodylumen. For example, FIG. 14A shows a balloon catheter 82 including acompliant balloon 86 having a smooth outer surface, which may limit theability of the balloon 86 to remove materials that are adherent to awall of a body lumen.

To increase traction, as shown in FIGS. 14B-14D, a balloon catheter 82′may be provided that includes a compliant, low pressure balloon 86′ anda traction sheath 112. The balloon 86′ may be provided on a distal end82 b′ of the catheter 82,′ similar to other embodiments herein, and thetraction sheath 112 may be received concentrically over the catheter 82′and/or over the balloon 86.′ In the embodiment shown, the tractionsheath 112 includes a tubular body carrying an expandable mesh 114 onits distal end. The traction sheath 112 may be movable axially relativeto the catheter 82,′ e.g., such that the expandable mesh 114 mayselectively surround at least a portion of the balloon 86.′ Initially,during a procedure, the expandable mesh 114 may be provided adjacent tothe balloon 86,′ i.e., without covering any portion of the balloon 86.′

If the balloon 86′ alone does not remove sufficient thrombus or othermaterial from a body lumen, as desired, the traction of the balloon 86′may be increased by advancing the traction sheath 112 from a firstposition proximal to the balloon 86,′ as shown in FIG. 14C, to a secondposition wherein the mesh 114 is disposed at least partially over theballoon 86,′ as shown in FIG. 14D. The balloon catheter 82′ may includean actuator on its proximal end (not shown) for directing the tractionsheath 112 between the first and second positions. Alternatively, theactuator may allow the traction sheath 112 to be directed to multiplepositions, e.g., to cover the balloon 86′ with as much of the expandablemesh 114 as desired. In a further alternative, the traction sheath 112may be attached or fixed to the catheter 82′ such that the expandablemesh 114 covers a predetermined portion of the balloon 86.′

The mesh 114 may provide a rough surface that may be pushed into orotherwise enhance engagement with material to be removed from the bodylumen using the inflated balloon 86.′ Furthermore, the amount of tensionthat may be applied to the traction sheath 112 may be higher than thatof the balloon 86′ alone, because the traction sheath 112 is constructedof thicker and/or stronger materials than the compliant balloon 86.′ Themesh 114 on the traction sheath 112 may be constructed of a variety ofmaterials, including a hollow braid of metal or polymer strands, apolymer or metal tube cut with a plurality of apertures to form astent-like structure, or a series of longitudinal struts composed ofmetal or plastic that remain substantially parallel to each other duringtheir initial advancement over the balloon 86.′

Turning to FIGS. 15A and 15B, a sheath 20 is shown that includes a lumen24 and an expandable member 26 a, similar to the other embodimentsherein. As will be appreciated, the lumen 24 of the sheath 20 mustaccommodate a guidewire, a treatment device, such as balloon catheter 82(not shown), as well as material being captured or removed using thetreatment device. Given that these devices occupy space within the lumen24, the sheath 20 may be limited in how large the particles are that thesheath is able to receive. FIGS. 15A and 15B show an alternativeembodiment of a guidewire 164 that may be used in conjunction with thesheath 20 and/or apparatus 10 (not shown), which may be any of theembodiments described herein. Thus, the guidewire 164 may be included aspart of a system including the apparatus 10 and/or any of the treatmentdevices described herein or in the references incorporated by referenceherein.

In one embodiment for maximizing the ability of the sheath 20 to removelarge particles, the space that the guidewire occupies within the lumen24 of the sheath 20 may be minimized. Relatively larger guidewires(e.g., approximately 0.035 inches in diameter) are commonly used due totheir high levels of support for devices tracked over them. FIG. 15Ashows an alternative embodiment of a guidewire 164 over which a sheath20 has been advanced. The guidewire 164 includes an inner portion orcore 168 over which an outer portion or sleeve 166 is slidably disposed.With the sleeve 166 positioned over the core 168, the guidewire 164 mayhave properties similar to other guidewire, e.g., allowing the guidewire164 to be introduced easily through a needle or other instrument into agraft lumen 50 or other body lumen, e.g., similar to the process shownin FIG. 5. Once the guidewire 164 is positioned sufficiently into thegraft lumen 50, an apparatus 10 (not shown) including sheath 20 may beadvanced over the guidewire and into the graft lumen 50, similar to theembodiments shown in FIGS. 6 and 7. If desired, the guidewire 164 may bemanipulated further if not already positioned, e.g., such that thedistal end of the guidewire 164 extends beyond thrombus or othermaterial to be removed or treated, e.g., as shown in FIG. 8.

Once the sheath 20 and guidewire 164 are in place, the sleeve 166 of theguidewire 164 may be removed, leaving behind the relatively smalldiameter core 168 of the guidewire 164, as shown in FIG. 15B. Thissmaller guidewire 168 occupies less space inside the lumen 24 of thesheath 20 and, thereby allows larger particles to be drawn into thelumen 24, e.g., using an embolectomy balloon catheter or other treatmentdevice, such as those described elsewhere herein. In this embodiment,the treatment device may have a relatively small accessory lumen toslidably accommodate the core 168 of the guidewire 164 therein, andtherefore the shaft of the treatment device may also have a relativelysmall outer diameter compared to a device that is advanced over a largerguidewire. Thus, the smaller guidewire 164 and consequent treatmentdevice shafts may leave more room within the lumen 24 to remove largerparticles from of the body lumen.

Turning to FIGS. 16A-16C, another embodiment of a sheath 120 is shownthat may increase the ability of the sheath 20 to remove relativelylarge particles. Generally, the sheath 120 may include features similarto the other embodiments described herein, and may be incorporated intothe apparatus 10 shown in FIGS. 1A-3 or any other apparatus or system.For example, the sheath 120 includes a shaft 122 carrying an expandablemember 126 a, which may be constructed and used similar to the previousembodiments.

Unlike the previous embodiments, at least a portion of the shaft 122 ofthe sheath 120 may be radially expandable to accommodate a relativelylarge particle 116 passing therethrough, as shown in FIG. 16A. In thisexample, an embolectomy balloon 86 is being used to pull the particle116 through the sheath lumen 24 and out of a body lumen and a patient'sbody.

As shown in more detail in FIG. 16B, the shaft 122 of the sheath 120 mayinclude an inner layer 152 constructed from one or more substantiallyinelastic material, e.g., for providing desired structural rigidity tothe sheath 120. One or more slots 154 may be provided in the inner layer152, e.g., extending along the entire length of the sheath 120 or onlyalong a distal portion of the sheath 120, for example, if the sheath 120include a relatively large diameter proximal portion. The shaft 122 alsoincludes an outer shaft layer 156, which may be constructed from one ormore elastic materials that provide a fluid-tight outer skin for theshaft 122, e.g., to prevent fluid from passing through the slot(s) 154in the inner layer 152. If a radially-outward force is applied, e.g.,the slot(s) 154 may open and the outer layer 156 may elastically deformto allow radial expansion of the shaft 122. When the radially-outwardforce is removed, the outer layer 156 may resiliently return inwardly tothe original size, closing the slot(s) 154.

As shown, the outer layer 156 may be an enclosed sleeve surrounding theinner layer 152. The outer layer 156 may be attached to the inner layer152, e.g., to an outer surface of the inner layer 152, for example, byinterference fit, by bonding with adhesive, sonic welding, heat fusing,and the like. Alternatively, the elastic layer 156 may be bonded to theinside diameter of the inelastic layer 152 (not shown), which mayprovide a harder and/or more lubricious outer surface for the sheath120, if desired. In an alternative embodiment, the elastic layer may bebonded to an inside surface of the slotted layer.

During use, a treatment device, such as balloon catheter 82 shown inFIG. 16A may be used to draw thrombus or other material 116 into thelumen 124 of the sheath 120, similar to the previous embodiments. If thematerial 116 is larger than the diameter of the lumen 124 with the outerlayer 156 in its relaxed or relatively low potential energy state, thenpulling the material 116 into the lumen 124 may cause the outer layer156 to stretch, thereby opening the slot(s) 154 and increasing thediameter of the inner layer 152 and shaft 122. As the material 116passes along the expandable portion of the shaft 122, the shaft 122 mayresiliently expand and contract back towards the relaxed state, as canbe seen in FIG. 16A.

Turning to FIG. 16C, another embodiment of a sheath 120′ is shown (withan expandable member not shown merely for convenience) that includes analternative radially expandable shaft 122′. Instead of one or moreelongated slots along the entire length of expandable portion of theshaft 122,′ a plurality of discrete length slots 158′ may be provided ina relatively inelastic layer 152,′ e.g., similar to a slotted-tubestent. An elastic layer (not shown) may again be provided on the outsideor inside of the inelastic layer 152.′ The slots 158′ may be formed inthe wall of the inelastic layer 152,′ e.g., by cutting the slots 158′into a tube, e.g., by laser cutting, mechanical cutting, or by cuttingthe slots in a sheet and rolling and attaching longitudinal edges of thesheet (not shown). The material of the inelastic layer 152′ may besufficiently flexible to accommodate deformation of the inelastic layer152,′ e.g., such that radial expansion of the shaft 122′ may occursimilarly to the opening of a stent as oversized material is pulledthrough the lumen 124.′ The elastic layer may resiliently bias theinelastic layer 152′ and consequently the shaft 122′ to return inwardlytowards the relaxed or smaller diameter.

It will be appreciated that elements or components shown with anyembodiment herein are exemplary for the specific embodiment and may beused on or in combination with other embodiments disclosed herein.

While the invention is susceptible to various modifications, andalternative forms, specific examples thereof have been shown in thedrawings and are herein described in detail. It should be understood,however, that the invention is not to be limited to the particular formsor methods disclosed, but to the contrary, the invention is to cover allmodifications, equivalents and alternatives falling within the scope ofthe appended claims.

What is claimed is:
 1. An apparatus for removing obstructive materialfrom a body lumen and for dilating the body lumen, the apparatuscomprising: a tubular member having a proximal end, a distal end, and afirst lumen extending between the proximal and distal ends; anexpandable member at the distal end of the tubular member, theexpandable member including an inner membrane and an outer membranesurrounding the inner membrane such that the inner and outer membranesdefine a substantially enclosed interior, the expandable member beingexpandable between a collapsed configuration and an expandedconfiguration, wherein, with the expandable member in the expandedconfiguration, the inner membrane has a concave axial cross-section andthe outer membrane has a convex axial cross-section such that theexpandable member has a tapered shape that flares outwardly away fromthe proximal end to define an inlet that is larger than and fluidlycommunicates with the first lumen; an inner member having a proximal endand a distal end having a tapered profile, the inner member beingremovably disposed within the first lumen of the tubular member suchthat the inner member proximal end extends proximally from the tubularmember proximal end and a tapered distal tip of the inner member extendsdistally beyond the tubular member distal end; and a treatment membersized to be introduced through the first lumen of the tubular memberafter removal of the inner member, the treatment member comprising anexpandable treatment element on a distal end thereof for treating anocclusive region within a body lumen within which the tubular member isdeployed.
 2. The apparatus of claim 1, wherein the expandable treatmentelement comprises a first balloon and a second balloon disposedconcentrically around the first balloon, wherein the first balloon ismore compliant than the second balloon.
 3. The apparatus of claim 1,wherein the tubular member comprises a second lumen extending betweenthe tubular member proximal and distal ends and in fluid communicationwith the substantially enclosed interior.
 4. The apparatus of claim 1,wherein the inner membrane has a shorter length than the outer membrane.5. The apparatus of claim 1, wherein the inner membrane comprises areinforcement layer that allows radial expansion and resists bending orcompression in an axial direction.
 6. The apparatus of claim 1, whereinthe inner member comprises a recess adjacent the tapered distal tip forreceiving a portion of the expandable member in the collapsedconfiguration.
 7. The apparatus of claim 1, wherein the inlet defines afirst diameter, when the expandable member is in the collapsedconfiguration, that is substantially equal to a diameter of the firstlumen, and defines a second diameter when the expandable member is inthe expanded configuration, the second diameter being larger than thefirst diameter, and the expandable member tapering from the seconddiameter proximally towards the first diameter.
 8. The apparatus ofclaim 1, wherein the inner membrane of the expandable member defines atapered conical shape in the expanded configuration.
 9. An apparatus fortreating a body lumen, the apparatus comprising: a sheath having aproximal end, a distal end sized for introduction into a body lumen, anda first lumen extending between the proximal and distal ends; anexpandable member at the distal end of the sheath, the expandable memberincluding an inner membrane and an outer membrane surrounding the innermembrane such that the inner and outer membranes define a substantiallyenclosed interior, the expandable member being expandable between acollapsed configuration and an expanded configuration, wherein, with theexpandable member in the expanded configuration, the inner membrane hasa concave axial cross-section and the outer membrane has a convex axialcross-section such that the expandable member defines a distal openingcommunicating with the first lumen, and the expandable member tapersfrom a first diameter at the distal opening to a second diameter similarto the first lumen, the first diameter being larger than the seconddiameter; and a dilator slidably disposed within the first lumen, thedilator having a proximal end adjacent the sheath proximal end, atapered distal tip extending beyond the sheath distal end, and anannular recess that receives a distal end of the expandable member whenthe expandable member is in the collapsed configuration.
 10. Theapparatus of claim 9, wherein the first diameter is configured to besubstantially equal to or greater than an inner diameter of the bodylumen within which the expandable member is expanded, such that theexpandable member engages a wall of the body lumen when the expandablemember is in the expanded configuration.
 11. The apparatus of claim 9,wherein at least a portion of the sheath is radially expandable from arelaxed cross-section to an enlarged cross-section to accommodatereceiving material larger than a cross cross-section of the first lumen.12. The apparatus of claim 9, further comprising an elongate treatmentmember configured for introduction through the first lumen for treatingan obstructive region of the body lumen within which the sheath isintroduced.
 13. An apparatus for treating a body lumen, the apparatuscomprising: a tubular member including a proximal end, a distal end, afirst lumen extending between the proximal and distal ends, and aninflation lumen extending between the proximal and distal ends; anexpandable member at the distal end of the tubular member, theexpandable member including an inner membrane and an outer membranesurrounding the inner membrane such that the inner and outer membranesdefine a substantially enclosed interior, the expandable member beingexpandable between a collapsed configuration and an expandedconfiguration, wherein, with the expandable member in the expandedconfiguration, the inner membrane has a concave axial cross-section andthe outer membrane has a convex axial cross-section such that theexpandable member has a tapered profile that tapers from a firstdiameter at a distal opening proximally towards a second diameter,wherein the first diameter is greater than the second diameter; and aninner member slidably disposed within the first lumen, the inner membercomprising a proximal end adjacent the tubular member proximal end, anda tapered distal tip extending distally beyond the tubular member distalend.
 14. The apparatus of claim 13, wherein the inner member comprisesan annular recess adjacent the tapered distal tip, and wherein a portionof the expandable member, when in the collapsed configuration, fitswithin the annular recess.
 15. The apparatus of claim 13, wherein theinflation lumen fluidly communicates with the enclosed interior, andwherein the apparatus further comprises an inflation port on the tubularmember proximal end for delivering inflation media into the inflationlumen and to the enclosed interior for expanding the expandable member.16. The apparatus of claim 13, wherein the inner membrane comprises areinforcement layer.
 17. The apparatus of claim 16, wherein thereinforcement layer is formed of a material that is resistant to bendingor compression in an axial direction relative to the tubular member. 18.The apparatus of claim 13, wherein the outer membrane has a length thatis greater than a length of the inner membrane.
 19. The apparatus ofclaim 13, further comprising an elongate treatment member configured forintroduction through the first lumen for treating an obstructive regionof a body lumen within which the tubular member is introduced.
 20. Theapparatus of claim 19, wherein the elongate treatment member comprisestwo concentric expandable members on a distal end thereof.